This invention is directed to liquid ophthalmic pharmaceutical vehicles which become viscous on contacting the eye. This invention also relates to topical ophthalmic compositions comprising the vehicle and a pharmaceutically active drug.
It is known that the addition of viscous or visco-elastic polymers to an eye drop pharmaceutical composition, will increase the viscosity of the composition. This is usually desirable on the premise that an increased vehicle viscosity enhances drug delivery and duration of action; see, for example, J. Pharm. Pharmacol., Vol.34, pp.464-466 (Jan. 7, 1982). However, it is frequently advantageous to administer ophthalmic compositions as a drop, that is, an aqueous solution or suspension rather than a thick, viscous gel or ointment which can be messy and may tend to blur vision. In addition, non-droppable compositions can present problems with patient compliance, especially with the elderly.
The present invention provides for ophthalmic compositions which can be administered as a drop, but whose viscosity increases upon instillation into the eye so that the composition provides for relatively better drug delivery and duration of action, referred to herein as bioavailability, of drug over aqueous compositions whose viscosity does not increase upon instillation.